Was it because of the increased gravitational effect of his enlarged mass?

I was thinking about this the other day, that TOS mains sometimes didn't have much of a career after the show. Shatner did, of course, & Takei. Nimoy & Koenig, kind of (the latter taking some years to really ramp up again). Kelley, Doohan & Nichols...far less so. I don't think it was typecasting but almost an inability of the industry to see them in anything BUT that role.

This is pretty much the definition of typecasting though...

I suppose. Perhaps what I meant to say was that the industry believed the populace would have trouble seeing them in other roles.